Electroplating of beryllium



United States Patent ELEC'I'ROPLATING 0F BERYLLIUM Joseph J. Utz,Whittier, Caiifi, assignor, by direct and mesne assignments, to theUnited States of America as represented by the United States AtomicEnergy Commission N0 Drawing. Application July 12, 1954, Serial No.442,903

4 Claims. 01. 204-32 This invention relates to a method ofelectroplating various metals on beryllium. More particularly, thisinvention relates to a pretreatment of beryllium or beryllium alloysurfaces to insure a good bond between the beryllium base and theplating metal.

The preplating treatment of beryllium and the alloys containing a majorportion of beryllium has been found to be very critical. Conventionalacid and alkaline etching methods, both immersion and electrolytic,uniformly fail to allow satisfactory adhesion of the electrodeposits.Various other methods of coating beryllium have been attempted withoutattaining the desired results. These methods include carbonyl reduction,iodide reduction, roll cladding, and weld jacketing.

The essence of this invention is in providing an electrodeposited firstlayer on the beryllium base metal which establishes a sound metallicbond between such base metal and that layer. The nature of the firstelectrodeposited layer is such that various metals may be plated thereonby conventional plating techniques.

The principal object of this invention is to provide a method of platingvarious metals on beryllium and its alloys.

A further object of this invention is to provide a method of pretreatingthe surface of beryllium and its alloys prior to conventional platingprocedures.

A still further object of this invention is to provide a method ofdepositing a preliminary electrodeposited layer on beryllium.

An additional object of this invention is to provide a smooth, dense,homogeneous metallic layer on beryllium having the characteristic visualqualities associated with conventional nickel plates.

A further object of this invention is to provide an electrolyticpreplating treatment for beryllium and its alloys.

A still further object of this invention is to provide a uniform,strongly bonded coating on beryllium metal objects.

An additional object of this invention is to provide an intermediatebonding agent for plating conventional metals on beryllium and itsalloys.

Other objects of invention will become apparent from the followingdescription.

Various types of beryllium and beryllium alloys may be treated by theinstantly disclosed process. The process has been found to beparticularly applicable to wrought beryllium but may also be used withsintered powdered compacts and vacuum cast extruded beryllium. Thedisclosure and claims comprehend the inclusion of pure beryllium,beryllium alloys, beryllium compacts, as well as various objects ofberyllium in the broad term beryllium used in the specification andclaims.

The basic invention basically comprises the steps of cleaning theberyllium surface, placing a cobalt strike on said surface andconventionally electroplating on said cobalt surface. It has been foundthat it is necessary to thoroughly clean the surface prior to the cobaltstrike.

2,798,036 Patented July 2, 1957 The cobalt strike should be appliedimmediately after the cleaning operations. The cleaning is done byrinsing the beryllium in clean acetone, normally at room temperature,for a few minutes. Other ketones, such as diethylketone or methylethylketone may be used in this degreasing and activation step. Normallythe ketone rinsing will be for a period of from 3 to 5 minutes. Afterthe ketone rinse the beryllium material is water rinsed for a period ofapproximately 1 minute at a temperature from 20 to 40 C. The time lagbetween the ketone rinse and the water rinse must not be so great thatthe ketone film is allowed to evaporate exposing dry beryllium. Thus theketone provides an air barrier on the surface of the beryllium. Caremust be taken that the water rinse contains no contaminants to interferewith the cobalt strike.

A particular composition of matter has been formulated for the cobaltstrike. This striking bath is made up of cobalt sulfate of the hydrousor anhydrous type in the proportions of 0.2 molar-0.6 molar and ammoniumsulfate in similar proportions. The cobalt sulfate and ammonium sulfateare made up in an aqueous solution which has high chemical stability.The bath is normally operated at room temperature without externalfacilities for either heating or cooling. The bath, however, may be inthe temperature range of 1040 C. The plating bath is maintained at acurrent density of from 25 to 45 amps. per sq. ft. and at a pH of from46. Normally stainless steel or carbon anodes are used and the metalliccobalt is plated directly from the bath. Such carbon anodes are in theform of bagged graphite.

The cobalt strike is normally carried out for a period of from 1 to 5minutes dependent upon the thickness of the coat desired. It is to beunderstood that if thicker coats are desired the time within the cobaltstrike bath will be increased.

The following example shows a specific formulation of a cobalt strikesolution and operating conditions which are usable to deposit a 0.00075inch layer of cobalt on various beryllium objects. Hydrous cobaltsulfate in the amount of 126 grams per liter (0.45 M) and 59.4 grams perliter (0.45 M) of ammonium sulfate were made up in an aqueous solution.The strike was made at room temperature (24 C.) at a current density of25 amps. per sq. ft. using stainless steel anodes. After the berylliumhad been rinsed for approximately 3 minutes in clean acetone and quicklywater rinsed, the beryllium was placed in a cobalt strike bath forapproximately 3 minutes. A smooth, dense, homogeneous layer having thecharacteristic visual qualities associated with conventional nickelplates and of a thickness of 0.00075 inch resulted from suchpretreatment.

The above-described process provides an intermediate bonding agent whichwill allow various electrodeposited metals to adhere to beryllium. Suchmetals as copper, zinc, silver, chromium, and mckel may then beelectroplated directly on the cobalt bonding agent by conventionalelectroplating techniques.

By reason of the cleaning procedures and the cobalt strike from a bathhaving a cobalt-ammonia ion complex therein it is possible to adheringlyplate a variety of conventional metals on a beryllium substructure.

The instant process is usable wherever there is a need for soldering orotherwise attaching beryllium to itself or to other metals. For example,when the beryllium is used as a window or port in X-ray tubes, where itslow atomic number and density make the port pervious to even long waveX-rays, such beryllium much be attached to the remainder of the tube bysome means. The instant preplating treatment permits the edges of theberyllium port to be soldered to the tube structure due to the ease ofsoldering on the above-mentioned electrodeposited metals asdistinguished from straight beryllium. Likewise,zthe:non-sparkingrqualities of beryllium make such a -light, hard -metalapplicable ..for -shielding ,purposes in A.-C. motors developed for usein semi-hazardous or explosive atmospheres. Here also the instantinvention provides a means'for' attaching the -beryllium to other ;partsof the motor.

Theedges of beryllium oscillatingor stationary mirrors, which mirrorshave high reflectivity in ".the ultra-violet range, may :be treated :inthe manner prescribed :by the instantinvention to :provide both.solderable :surfaces and a tboundary surface to minirnize :the effectsof :galvanic action atlocalizedcontact areas-of 'the dissimilar metals.

Although the invention has been described and-illustrated in detail, itis :to beclearly understood that the same is by way :of illustration:and example only rand is not to be:taken by way of limitatiomthe spiritand scope of this invention being limited :onlyby theterms of theappended claims.

I claim:

1. The-method of pretreating beryllium compositions priortoelectroplating comprising degreasingsaid beryllium witha ketone, rinsingsaidberyllium in water prior to evaporationof said ketone, and thensubjecting the resulting water-wet beryllium toa cobalt strike in a bathcomprising from 0.2-0.6 molar cobalt sulfate and'from 0.2-0.6 molarammoniumsulfate.

2. The invention as described in claim 1 in which the ketone is acetone.

3. The invention as described in claim 1 in which the cobalt strikingbath is kept at a temperature of from 1040 C. and at a current densityof from 25-45 amps. per sq. ft.

4. A preplating treatment for beryllium and alloys containing a majorportion of beryllium, comprising degreasing said beryllium with aketone, rinsing said beryllium with water prior to evaporation of saidketone, and then subjecting the resulting water-wet beryllium to acobalt strike in a bath comprising an aqueous solution of cobaltsulphate and ammonium sulphate.

References Cited in the file ofthis patent UNITED STATES PATENTS Beachet a1 Ian. 3,.1956

4. A PREPLATING TREATMENT FOR BERYLLIUM AND ALLOYS CONTAINING A MAJORPORTION OF BERYLLIUM, COMPRISING DEGREASING SAID BERYLLIUM WITH AKETONE, RINSING SAID BERYLLIUM WITH WATER PRIOR TO EVAPORATION OF SAIDKETONE, AND THEN SUBJECTING THE RESULTING WATER-WET BERYLLIUM TO ACOBALT STRIKE IN A BATH COMPRISING AN AQUEOUS SOLUTION OF COBALTSULPHATE AND AMMONIUM SULPHATE.